Document everything in writing. Keep records of everything going on.
They don't respond to me, and choose to respond to others in the same conversation.
Don't go to meetings unprepared. Make notes about the topics you wish to discuss and ask compelling questions. Review your notes before the meeting and try to reduce them to the most important.
Try to stay on topic in meetings and ask questions from your prepared list. After the meeting bring your list to the meeting organizer and ask "Please explain why these questions were not answered".
Keep your notes for your records. If they continue to not answer your questions you can bring the list to your boss or higher up and ask "Please explain why these questions were not answered".
If you don't keep a record of what is happening in meetings, then it's like the meetings never happened. When a co-worker does not answer questions it becomes a disciplinary issue, and there is little they can do to explain why they wouldn't answer a valid question.
I am not invited to meetings where I did the work for something or am well-versed in how something works.
Make a list of everything you've worked on. For each item on the list create a sub-list of questions related to that work.
If you know the meeting is going to happen present the meeting organizer with your list. Inform them that you have questions that need answering. Give them a copy of the list, and ask to receive the answers in writing.
If the meeting happens without your awareness then bring the list to the organizer and ask them to schedule another meeting to address your questions. Give them a copy of the list, and ask to receive the answers in writing.
If they don't answer the questions or the answers don't enable you to do your job, then bring these documents to your boss or higher up.
I am not asked about my thoughts on something where I've already shown I can do something.
Write it down.
Keep a log of all your ideas and how they would have improved the situation or provided a better solution. Don't write down anything negative about a coworker. Keep the logs on topic to the ideas only.
Review the log frequently and remove any ideas that someone can find fault with. You want a log of only ideas that can't be refuted.
When you have a long enough list of ideas and you feel comfortable with the list. Bring it to your boss or higher up. Ask why your ideas are being ignored.